<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #box{
            text-align: center;
            width: 500px;
            height: 100px;
            margin-left: 700px;
            color: aqua;
           
        }
        #tou{
            margin-left: 900px;
            text-align: center;
        }
    </style>
</head>
<body>
    <button onclick="fu()" id="tou" >点击</button>
    <div id="box">
    </div>
    <script>
        var dianji = document.querySelector('#dianji');
        var cishu = 0 ;
        function fu() {
            cishu++;
            document.getElementById('box').innerHTML = '封校三天 快乐无边';
            if (cishu%2==0){
                document.getElementById('box').innerHTML ='';
            }
        }
    </script>
</body>
</html>